Electrical Wire and Cable Size Calculator

Wire Cross-Sectional Area Formula:

\[ A = \frac{2 \times \rho \times L \times I}{VD} \]

Resistivity (ρ):

ohm-m

Length (L):

meters

Current (I):

amps

Voltage Drop (VD):

volts

Wire Cross-Sectional Area (m²):

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1. What is an Electrical Wire and Cable Size Calculator?

Definition: This calculator determines the minimum cross-sectional area of a wire needed to carry a specific current over a given distance while maintaining acceptable voltage drop.

Purpose: It helps electricians, engineers, and DIYers select the proper wire gauge for electrical installations to ensure safety and efficiency.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ A = \frac{2 \times \rho \times L \times I}{VD} \]

Where:

\( A \) — Cross-sectional area of wire (m²)
\( \rho \) — Resistivity of conductor material (ohm-m)
\( L \) — Length of wire (meters)
\( I \) — Current (amps)
\( VD \) — Maximum allowable voltage drop (volts)

Explanation: The formula calculates the minimum wire size needed to limit voltage drop to acceptable levels based on current and distance.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents excessive voltage drop (which can cause equipment malfunction), reduces energy loss, and minimizes fire hazards from overheating.

4. Using the Calculator

Tips:

Default resistivity (1.68×10⁻⁸ ohm-m) is for copper at 20°C
For aluminum, use 2.82×10⁻⁸ ohm-m
Typical voltage drop limits: 3% for branch circuits, 5% for feeders
Length should be the one-way distance (round trip is automatically calculated)

5. Frequently Asked Questions (FAQ)

Q1: How do I convert the result to AWG or mm²?
A: Use a wire gauge table to find the standard size that meets or exceeds your calculated area.

Q2: Why is the length multiplied by 2 in the formula?
A: This accounts for the round-trip path of current (out to load and back).

Q3: What affects wire resistivity?
A: Material (copper/aluminum), temperature, and conductor stranding affect resistivity.

Q4: Should I consider other factors besides voltage drop?
A: Yes, also check ampacity tables for current-carrying capacity based on insulation type and installation method.

Q5: What's a typical voltage drop allowance?
A: 3% for branch circuits, 5% for feeders is common, but check local codes for requirements.